Electron tube oscillator system



Oct. 24, 1933. J. a. DOW 1,931,530

ELECTRON TUBE OSCILLATOR SYSTEM Filed Feb. 10, 1931 INVENTOR. Jaws W 0 3), Dow,

T 5 BY a W ATTORNEY Patented Oct. 24, 1933 UNITED TAT s n Eo'raon runii g s ifim'ron SYSTEM PATENT OFFICE Jennings 3. Dow, Alexandria, Va.

'. Application February 10, 1931. Serial No. 514,848

' 14 Claims. (01. 250-36) (Granted under the act of March 3.1883, as

amended April 30, 1928; 370 0. G. 757) My invention relates broadly to electron tube oscillator systems and more particularly to a power oscillator tube system having a high degree of frequency stability.

One of the objects of my invention is to provide a stabilized oscillation circuit including an electron tube having a cathode, control grid, inner anode and outer anode, with means for compensating for the effects of electrostatic capacity existing between the inner and outer anode elements.

Another object of my invention is to provide a circuit arrangement for an oscillation system employing an electron tube having a cathode,

15 a control grid, an inner anode and an outer anode, with an adjustable capacity connected between the control grid and outer anode elements of the tube and adjustable to apply an alternating potential to the outer anode which is substanially equal in amplitude and opposite in phase to, that applied to the outer anode from the inner anode by virtue of the interelement capacity between. the inner and outer anodes.

Still another object of my invention resides in a circuit arrangement for interconnecting an oscillation circuit with a'power amplification circuit where the .oscillation circuit includes an electron tube having both inner and outer anodes with means for compensating for the undesirable coupling normally existent between the frequency determining portion of the circuit and the, output circuit of the oscillator terminating at the outer anode.

Other and further objects of my invention reside in the circuit arrangement for a high frequencyv electron tube oscillator as set forth more fully in the specification hereinafter following by reference to the accompanying drawing in which: I

Figure 1.shows a circuit arrangement for an electron tube oscillator controlled by a piezo electric crystal element embodying the principles of my invention; Fig. 2 shows a circuit arrangement embodying the principles of my invention and employing a resonant circuit' for determining the frequency of oscillation in the oscillation system; Fig. 3 shows a modified form of frequency control circuit arrangedaccording to the principles of my invention and 5 employing a resonant circuit for determining the oscillation period of the system; Fig. 4 ,illustrates another modified form of oscillator circuit embodying the principles of my invention, the circuit being controlled by means of a piezo electric crystal element; and Fig. -5 illustrates in the frequency determining portion.

a manner of coupling an oscillator generator constructed in accordance with my invention to the input system of a power amplifier.

I have found in employing an electron tube having a cathode, a control grid, an inner anode 80 and an outer anode inan oscillator system, that instability of the frequency arises due to the inherent electrostatic capacity existing between the inner and outer anodes of the tube. This electrostatic capacity results in undesirable coupling between the frequency-determining portion of the circuit and the output circuit of the oscillation system. Changes in the loading condition of the output circuit are therefore felt I I have found that the effect of this electrostatic capacity between the inner and outer anode elements is overcome and compensated by connecting a small variable capacity between the control grid and outer anode of the tube and suitably adjusting this capacity. Through the medium of this small variablecapacit'y a radio frequency potential is applied to the outer anode which is equal in amplitude and opposite in phase to the potential which is applied to the outer anode by virtue of the electrostatic capacity between the inner and outer anodes. When this electrical condition is met, the radio frequency potential which exists across the impedance in the output circuit is due solely to the electron flow to the outer anode and better frequency stability is obtained.

Referring to the drawing in detail, the electron tube which is connected in the oscillation "circuit is shown at 1, including the cathode 1a, 9

the .control grid lb, theinner anode 1c and the outer 'anode 1d. The grid circuit 2 of the'electron tube system includes the grid leak 4 extending between the control grid 1b and the cathode la. The output circuit is indicated'at 3 extending between the outer anode 1d and the cathode 1a. The output circuit 3 includes the source of potential '7, connected between the cathode 1a and the anode ldthrough impedance 9' across which the output from the oscillator may be derived. The cathode 1a is heated from the source 8. A connection is taken from the inner anode 10 to a point of positive potential at the source 7 through the impedance 6. A frequency control element such as an electromechanical vibrator, a mechanically vibratile element or a piezo electric crystal 10 is connected between the control grid 1b and the inner anode 10 for determining the oscillation frequency of the system. An adjustable condenser 11 is connected across the control grid 11) and the outer anode 1d and is variable to compensate for electrostatic capacity existing between the inner anode 1b and the outer anode 1d.

In Fig. 2, I have shown a resonant circuit 12 including an inductance 15 shunted by a variable condenser 14 and providing means for determinating the oscillation period of the system. In the circuit shown in Fig. 2, a blocking condenser 16 is provided for keeping the positive inner anode potential of! the control grid 1b. The adjustable condenser 11 connects between control grid 1b and outer anode 112 for compensating for capacity efiects between the inner and outer anodes. The other portions of the circuit in Fig. 2 are similar to the circuit arrangement of Fig. 1. I

In Fig. 3, I have illustrated a modified arrangement of oscillator circuit wherein the impedance 6 is eliminated from the circuit, thus simp1ifying.the circuit without sacrifice of the performance of the system. In this arrangement a tap 34 is taken from a potential nodal point on inductance 15 to a point on potential source 7. The variable condenser 11 serves to neutralize the effect of the capacity between the inner anode 1c and outer anode 1d.

In Fig. 4, a crystal controlled master oscillator circuit has been shown wherein the generic impedances 6 and 9 have been replaced by the inductance 22 and the tuned circuit 1'7. The lower end of the inductance 22 connects to a point of positive potential on source '7 and the upper end of the inductance 22 connects to the inner anode 1c and to one side of the piezo electric crystal element '10. The piezo electric crystal element 10 is connected in series with condenser 16 to the control grid lb as shown thereby preventing any possibility of the impression of positive potential on control grid 117 from the inner anode 10. A resonant circuit 17 including an inductance 19 shunted by a variable condenser 18 connects in series between anode 1d and cathode 1a through the high potential source 7. The condenser 11 is adjustable for compensating for inter-electrode capacities in the manner explained in connection with Figs. 1, 2 and 3. Battery 8 supplies cathodeheating potential to the cathode 1a. A negative bias is placed upon control grid 11) from battery 5. A high frequency by-pass condenser 21 connects around the high potential source '7 in the plate trol grid 1b of the oscillator tube 1.

circuit. ,Leads are taken as represented at 36 from the output circuit of the oscillator through condenser 20 for feeding any desired amplification system. a

In Fig. 5, I have illustrated a method of connecting an oscillation circuit to the input of a power amplifier with means for compensating for capacity efiects between the inner and outer anodes. The power amplifier tube has been shown at 24 having an input circiut 28 and an output circuit 29, the input circuit being biased through impedance 26 from battery 2'7. A blocking condenser 25 is connected between the output of the oscillator tube 1 and the input circuit of the power amplifier tube 24 for isolating the amplifier grid 24b and the variable capacity 11 from the high voltage source '7. This blocking capacity 25 is very important in high voltage circuits especially when the variable condenser 11 might suffer a voltage breakdown which would place a high positive potential on the con- The generic impedances 6 and 9 have been replaced by the source 33.

inductances 22 and 23. The input circuit 28 of the amplifier is connected across the output inductance 23 of the oscillator circuit. The cathode of tube 24 may be heated from a suitable Suitable by-pass condensers 31 and 32 are provided in the different portions of the amplifier circuit. The output circuit 29 contains a resonant system 30 from which tap connections extend to the succeeding amplification stage or transmission circuit. The variable capacity 11 is adjusted for compensating for the electrostatic capacity effects between the inner and outer anodes 1c and 1d of the oscillator tube 1.

I have found the circuit arrangement of my invention highly efficient in its operation and stable in maintenance of constant frequency oscillations.

While I have described my invention in certain preferred'embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

The invention herein described may be manufactured and used by or for the Government of I the United States of America for governmental purposes without the payment of any royalties thereon.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In an oscillation generator employing an electron tube having a cathode, a control grid, an inner anode, and'an outer anode, an output circuit extending between said outer anode and said cathode and including "a source of potential, an oscillator circuit one portion of which extends between said inner anode and said cathode and includes a source of potential and another portion of which extends between said control grid and said inner anode for determining the frequency of oscillation of said generator, and means connected between said control grid and said outer anode for compensating for the efiects of electrostatic capacity existent between said inner and outer anodes.

2. In an oscillation generator employing an electron tube having a cathode, a control grid, an inner anode and an outer anode, an output circuit extending between said outer anode and said cathode and including a source of potential, an oscillator circuit one portion of which extends between said inner anode and said cathode and includes a source of potential, and another portion of which extends between said control grid and said inner anode for determining the frequency of oscillation of said generator, and a variable impedance connected between said control grid and said outer anode for compensating for the effects of electrostatic capacity existent between said inner and outer anodes.

3. In a resonant oscillation generator employing an electron tube having a cathode, a control grid, an inner anode'and an outer anode, an output circuit extending between said outer anode and said cathode and including a source of potential, an oscillator circuit one portion of which extends between said inner anode and said cathode and includes a source of potential, and another portion of which extends between said control grid and said inner anode for determining the frequency of oscillation of said for compensating for the eflects of electrostatic capacity existent between said inner and outer anodes.

4. In an oscillation generator employing an electron tube having a cathode, a control grid, an inner anode and an outer anode, an output circuit extending between said outer anode and said cathode and including a source 01' potential, an oscillator circuit one portion of which extends between said inner anode and said cathode and includes a source of potential, and another portion of which includes a piezo electric crystal element included in circuit between said control grid and said inner anode for determining the frequency of oscillation of said generator, and a balancing condenser connected between said control grid and said outer anode for compensating for the eifects of electrostatic capacity existent between said inner and outer anodes.

5. In an oscillation generator employing an electron tube having a cathode, a control grid, an inner anode and an outer anode, an output circuit extending between said outer anode and said cathode and including a source of potential, an oscillator circuit one portion of which extends between said inner anode and said cathode and includes a source of potential, and another portion of which includes an electromechanical vibrator included in circuit between said control grid and said inner anode for determining the frequency of oscillation of said generator, and a balancing condenser connected between said control grid and said outer anode for compensating for the effects of electrostatic capacity existent between said inner and outer anodes.

6. In an oscillation generator employing an electron tube having a cathode, a control grid, an inner anode and an outer anode, an output circuit extending between said outer anode and said cathode and including a,source of potential. anoscillator circuit one portion of which extends between said inner anode and said cathode and includes a source of potential, and another portion of which includes a piezo electric crystal element included in circuit between said control grid and said inner anode for determining the frequency of oscillation of said generator, and a balancing impedance connected between said control grid and said outer anode for compensating for the effects of electrostatic capacity existent between said inner and outer anodes.

7. In an oscillation generator employing an electron tube having a cathode, a control grid, an inner anode and an outer anode, an output circuitextending between said outer anode and said cathode and including a source of potential, an oscillator circuit one portion of which extends between said inner anode and said cathode and includes a source of potential, and another portion of which includes an electromechanical vibrator included in circuit between said control grid and said inner anode for, determining the frequency of oscillation of said generator, and a balancing condenser connected between said control grid and said outer anode for compensating for the effects of electrostatic capacity existent between said inner and outer anodes.

8. In a transmission system, a poweramplifler, an electron tube having an oscillator portion including a cathode, a control grid, and an inner anode and having an output portion including an outer anode, an output circuit included between said outer anode and said cathode, a frequency determining element connected between said control grid and said inner anode, means for preventing undesirable coupling between said oscillator portion and said output circuit including a variable condenser connected between said control grid and a point in the input circuit of said power amplifier, and a blocking condenser disposed between the high potential portion of the output circuit of said oscillator tube and the input circuit of said power amplifier, said variable condenser being adjustable to compensate for the inherent capacity existing between the inner and outer anodes of said oscillator tube.

9. In a transmission system, a power amplifier, an electron tube having an oscillator portion including a cathode, a control grid and an inner anode and having an output portion including an outer anode, an output circuit included between said outer anode and said cathode, a piezo electric crystal element connected between said control grid and said inner anode, means for preventing undesirable coupling between said oscillator-portion and said output circuit including a variable condenser connected between said control grid and a point in the input circuit of said power amplifier, and a blocking condenser disposed between the high potential portion of the output circuit of said oscillator tube and the input circuit of said power ampliher, said variable condenser being adjustable to compensate for the inherent capacity existing between the inner and outer anodes of said oscillator tube.

10. In an oscillator system, an electron tube three electrodes of which, namely the cathode, the control grid and an inner anode, are included in an oscillator circuit and an outer anode of which is included merely in an output circuit, means for maintaining substantially constant the oscillation frequency 01 said system and means for compensating for the effects of electrostatic capacity existing between the inner and outer anodes.

11. A device in accordance with claim 10 in which a piezo-electric device is included in the first said means.

12. A device in accordance with claim 10 in which a resonant circuit is included in the first said means.

13. A device in accordance with claim 10 in which an adjustable capacity element is included in the last said means.

14. In an oscillator system, an electron tube having three electrodes included in a substantially constant frequency oscillator circuit and a fourth electrode included in an output circuit, and means including an adjustable capacity for applying an alternating potential to the fourth electrode which is substantially equal in existent between said fourth electrode and one] 

